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View Horde LLC's top competitors like Atmail, Collabora Productivity, and IceWarp.

Open-Xchange
Open-Xchange (OX) is a market leader of secure, open communication and office productivity software, email server software and DNS solutions, with hundreds of millions of users worldwide. As the leading independent email provider, we work with some of the world’s largest hosters, telcos and ISPs (including partners such as IONOS, KPN, Orange, Italiaonline, NTT, Softbank and TalkTalk), as well as public sector organizations. Our roots in open source have shaped our view of the world and culture – open, diverse, and with a bias to act, giving everyone at OX room to take responsibility within their team and grow. As a company, we believe in an internet that is open, safe and free, and create competitive products that allow our customers to deliver secure internet services with great user experience, and that respect privacy and generate value. With 230+ people worldwide, OX develops and operates open source software (aaS) for mail/messaging and collaboration/productivity. Dovecot is the world’s most popular IMAP server software, and PowerDNS provides secure DNS services to our customers and their users. Our business is fast-paced and changing constantly. We are always looking for people who share our vision, who want to make a difference, thrive in agile, non-hierarchical environments, and enjoy working in a high-tech environment as part of a truly international team. OX is headquartered in Cologne, Germany, with further offices in Hamburg, Nuremberg and Olpe), in addition to the USA (Palo Alto, CA, and New York, NY), Finland (Espoo), The Netherlands (The Hague), Italy (Turin), and Japan (Tokyo). If you're interested in joining OX, please visit: https://ox.io/careers
Köln, DE
Private
$32.4M Revenue
https://www.ox.io
199 Employees
Zimbra
Zimbra offers businesses a secure, data-sovereign email and collaboration platform built on open standards. A low-risk alternative, it provides integrated email, calendar, contacts, tasks, and document sharing. Businesses gain complete control over their data with flexible on-premises or cloud deployment options, ensuring compliance and avoiding vendor lock-in. Empowering productivity with advanced security, Zimbra delivers a trusted and transparent communication solution designed for your needs.
SG
Private
$68.1M Revenue
https://www.zimbra.com
123 Employees
IceWarp
Unified Email & Collaboration Hub. Secure professional email on own domain and revolutionary integration with chats. Shared calendars for smooth planning. Real-time collaboration for every team and project with TeamChat. Cloud storage so all your files are available anytime on all your devices. Online documents with easy sharing and collaborative editing. Desktop and Mobile apps. Completely developed in-house since 2001. With flexible development ensures ongoing development and fast support. Our goal is to always innovate through our services according to current trends and feedback from more than 50,000 actual customers.
CZ
Private
$15.6M Revenue
http://www.icewarp.com/
131 Employees
G2 Leader Summer 2026 G2 Best Est ROI Mid-Market Summer 2026 G2 Easiest Admin Mid-Market Summer 2026 G2 Most Implementable Summer 2026 G2 Best Results Mid-Market Summer 2026 G2 Lead Capture Mid-Market Summer 2026 Inc Fastest Growing Private Companies 2026 Inc Best Workplace 2026
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300K+ Plugin Users